JPH03216261A - Manufacture of cast steel pipe exhaust manifold - Google Patents

Abstract

PURPOSE:To omit the welding of a flange and to manufacture the above exhaust manifold at a low cost by pouring molten metal in a mold while heating end parts of a cast steel pipe inserted in the mold from inside and casting the flange as cast-in at outside of the end part of pipe. CONSTITUTION:The cast steel pipe 5 is cast under condition of the straight pipe and also after forming plural small circular recessed parts 5a at the time of casting this, this is bent to the prescribed shape. Successively, the end part at engine side of bent cast steel pipe 5 is set in through hole 2c in the casting mold 2, and the part at out of the mold in the cast steel pipe 5 is supported with a pipe receiving jig 4, and also the upper and lower molds 2a, 2b are mated. Successively, ignited gas burner 3 is inserted into the through hole 2c to heat the end part of cast steel pipe 5. After that, molten cast steel is poured into the cavity 2d from a sprue under condition of igniting the gas burner 3, and after pouring the molten steel, the gas burner 3 is extingushed and the cast molten steel is cooled. Then, the flange is fitted to the end part at the engine side of cast steel pipe 5 and cast as cast-in. Further, a collective flange 6 is cast to the other end part of cast steel pipe at the same time.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a manufacturing method suitable for manufacturing an exhaust manifold using cast steel pipes.

(Prior Art) As a conventional exhaust manifold, for example, there is one shown in FIG. are each provided with a mounting flange lb for attaching them to the engine side, while a collecting flange lc is provided at the other end of the three pipes to collect the pipes and connect them to the exhaust pipe.

In the past, when manufacturing such an exhaust manifold 1, the three pipes 1a, the mounting flange 1b, and the collecting flange 1c made of cast steel were usually cast as one piece. Because there is a large difference in wall thickness, gas defects such as poor water circulation and pinholes are likely to occur.Also, the exhaust manifold 1 is quite large as a whole and has a complicated shape, so it is difficult to A large number of man-hours were required to remove the flash that was generated.

For this reason, conventionally, as shown in FIG. 4, three straight cast steel pipes 1a are cast and then bent into a predetermined shape, and the mounting flange lb and gathering flange 1c are separately cast. A mounting flange 1b is welded to one end of the three cast steel pipes 1a at a welding part 1d, while a gathering flange 1c is attached to the other end of the three cast steel pipes.
Welded at welding part 1e, 1-1 manifold l"
1 was also implemented.

(Problem to be solved by the invention) However, as mentioned above, the method of welding flanges Ib and lc to the cast steel vibrator 1a also has the problem of increasing the number of welding steps because there are a large number of welded parts. there were.

The present invention provides a manufacturing method that advantageously solves these problems.

(Another Means to Solve the Problem) The method for manufacturing a cast steel pipe exhaust manifold of the present invention is as follows:
The end of the cast steel pipe inserted into the mold is heated from the inside with a gas burner, and the cast steel is poured into the mold, and a flange is cast on the outside of the end of the pipe. This is a characteristic feature.

(For bamboo) According to this force method, when casting mounting flanges and gathering flanges, those flanges are cast directly onto the end of a cast steel pipe that is cast in a straight pipe state and then bent into a predetermined shape. The man-hours for welding the flanges can be omitted, and therefore the exhaust eyebrow hold can be manufactured at low cost.

Moreover, according to this method, the flange is cast while heating the end of the cast steel pipe, so the weldability between the cast steel pipe and the flange is extremely good, and therefore high joint strength can be obtained. Since there is almost no gap with the pipe, no flash is generated along the pipe, and the flash can only be removed from around the flange, so the number of finishing steps is extremely small.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 is a sectional view taken along line I-1 of a casting mold for a mounting flange whose vertical cross section is shown in FIG. Reference numeral 2 indicates a casting mold for the mounting flange, 3 indicates a gas burner, 4 indicates a pipe receiving jig, and 5 indicates a cast steel pipe.

In this example, an exhaust eyebrow hold having two cast steel pipes per cylinder is manufactured for an engine having two exhaust valves per cylinder, and the casting mold 2 for the mounting flange is a sand mold. The casting mold 2 can be divided into an upper mold 2a and a lower mold 2b at a parting line indicated by the symbol A, and a gas burner 3 and a cast steel pipe 5 are connected to each other along the parting line A. A through hole 2c is provided for insertion into the mold from the opposite direction.

Moreover, in this casting mold 2 for the mounting flange, two cast steel vipes 5 are installed together to the engine side so as to surround one end of the cast steel vibrator 5 inserted into the through hole 2c as shown in the figure. A cavity 2d having the same shape as the mounting flange is provided, as well as a sprue 2e for pouring molten cast steel into the mold, and a runner 2f for communicating the in-situ spout 2e with the cavity 2d.

Using such a casting mold 2, a mounting flange is formed at one end of a cast steel pipe 5 in the following manner.

That is, first, the engine side end of the cast steel pipe 5 is cast in the form of a straight pipe, and at the time of casting, a large number of small circular recesses 5a are formed around both ends to further increase the bonding strength, and then bent into a predetermined shape. , Divided casting mold 2
The outside part of the cast steel pipe 5 is supported by the pipe receiving jig 4, and the upper and lower molds 2a and 2b are matched.

Next, the lit gas burner 3 is inserted into the through hole 2C, and the flame 3a of the gas burner 3 sufficiently heats the end of the cast steel pipe 5 to, for example, about 800''C.

Thereafter, with the gas burner 3 still lit, molten metal is poured into the cavity 2d from the sprue 2e, and immediately after the pouring is finished, the gas burner 3 is extinguished and the cast steel pipe 5 is turned off.
The end portion of the molten metal is cooled together with the molten metal.

Then, when the molten cast steel is solidified, the casting mold 2 is split and the mounting flange formed in the cavity 2d is taken out.

By this method, a mounting flange can be cast in the engine side end of the cast steel pipe 5, and thereafter, the other ends of the plurality of sets of cast steel pipes 5 each having a mounting flange provided at the engine side end are cast using the above method. Then, as shown in phantom lines in FIG. 1, a collecting flange 6 for collecting the pipes and connecting them to the exhaust pipe is cast in the same manner as described above.

Therefore, according to the method of this embodiment, when casting the mounting flange or gathering flange, the flanges are cast directly onto the end of the cast steel pipe which is cast in a straight pipe state and then bent into a predetermined shape. The man-hours for welding can be saved, and the exhaust manifold can be manufactured at low cost.

Furthermore, according to this method, the flange is cast while heating the end of the cast steel pipe, so that the weldability between the cast steel pipe and the flange is extremely good, and high joint strength can be obtained.

In addition, by heating the end of the cast steel pipe, for example, an outer diameter of φ4
When a 8.6 pipe is heated to 800°C, its radius increases by approximately 0.24 nv++, and the end of the pipe expands thermally, leaving almost no gap between the mold and the cast steel pipe. There is no casting flash along the mold, therefore the flash only needs to be removed from around the flange along the parting line of the mold, and the number of finishing steps can be extremely reduced.

Furthermore, in this embodiment, a large number of small circular recesses 5a are formed around the end of the cast steel pipe, so that the bonding strength of the cast steel pipe to the mounting flange or gathering flange can be further increased.

The above description has been made based on the illustrated example, but the present invention is not limited to the above example. For example, the recess may be a circumferential annular groove instead of a circle, and even in that case, it is difficult to pull out. It can bring strength.

Further, according to the method of the present invention, a shape different from the above example,
For example, it is of course possible to manufacture an exhaust mound hold having a shape as shown in FIG.

(Effects of the Invention) Thus, according to the method for manufacturing a cast steel pipe exhaust manifold of the present invention, the man-hours for welding the flanges can be omitted, so the exhaust manifold can be manufactured at a low cost, and moreover, the cast steel pipe and the flange can be manufactured at low cost. Because of the extremely good weldability, high joint strength can be obtained.Also, since there is almost no gap between the mold and the cast steel pipe, no flash is generated along the pipe, so the removal of flash is essentially a matter of removing the flange. Only the surrounding area is required, and the number of finishing steps can be extremely reduced.

[Brief explanation of drawings]

FIG. 1 is a sectional view taken along the I-f line in FIG. 2 of a casting mold for a mounting flange used in an embodiment of the method for manufacturing a cast steel pipe exhaust eyebrow hold of the present invention, and FIG. 2 is a sectional view of the casting mold for the mounting flange described above. FIGS. 3 and 4 are plan views showing exhaust manifolds manufactured by conventional methods, respectively. 2 Casting mold for mounting flange Upper mold cavity Runway Flame cast steel pipe gathering flange 2b 1 Lower mold 2e 1 Sprue 3 - Gas inlet 4 - Pipe receiving jig 5a - 1. Recess A - 1 parting line

Claims (1)

[Claims] 1. Heat the end of a cast steel pipe inserted into a mold from the inside with a gas burner, pour molten steel into the mold, and cast a flange on the outside of the end of the pipe. A method for manufacturing a cast steel pipe exhaust manifold, characterized by: